Fix `undefined-loop-variable` from walrus in comprehension test (#7324)

4 files changed, 31 insertions, 0 deletions

diff --git a/doc/whatsnew/fragments/7222.bugfix b/doc/whatsnew/fragments/7222.bugfix
new file mode 100644
index 000000000..0d18e73da
--- /dev/null
+++ b/doc/whatsnew/fragments/7222.bugfix
@@ -0,0 +1,3 @@
+Fix `undefined-loop-variable` from walrus in comprehension test.
+
+Closes #7222
diff --git a/pylint/checkers/variables.py b/pylint/checkers/variables.py
index e6af22689..3249a4b36 100644
--- a/pylint/checkers/variables.py
+++ b/pylint/checkers/variables.py
@@ -2249,6 +2249,24 @@ class VariablesChecker(BaseChecker):
         ):
             return
 
+        maybe_walrus = utils.get_node_first_ancestor_of_type(node, nodes.NamedExpr)
+        if maybe_walrus:
+            maybe_comprehension = utils.get_node_first_ancestor_of_type(
+                maybe_walrus, nodes.Comprehension
+            )
+            if maybe_comprehension:
+                comprehension_scope = utils.get_node_first_ancestor_of_type(
+                    maybe_comprehension, nodes.ComprehensionScope
+                )
+                if comprehension_scope is None:
+                    # Should not be possible.
+                    pass
+                elif (
+                    comprehension_scope.parent.scope() is scope
+                    and node.name in comprehension_scope.locals
+                ):
+                    return
+
         # For functions we can do more by inferring the length of the itered object
         try:
             inferred = next(assign.iter.infer())
diff --git a/tests/functional/u/undefined/undefined_loop_variable_py38.py b/tests/functional/u/undefined/undefined_loop_variable_py38.py
new file mode 100644
index 000000000..5778df7d2
--- /dev/null
+++ b/tests/functional/u/undefined/undefined_loop_variable_py38.py
@@ -0,0 +1,8 @@
+"""Tests for undefined-loop-variable with assignment expressions"""
+
+
+def walrus_in_comprehension_test(container):
+    """https://github.com/PyCQA/pylint/issues/7222"""
+    for something in container:
+        print(something)
+    print([my_test for something in container if (my_test := something)])
diff --git a/tests/functional/u/undefined/undefined_loop_variable_py38.rc b/tests/functional/u/undefined/undefined_loop_variable_py38.rc
new file mode 100644
index 000000000..85fc502b3
--- /dev/null
+++ b/tests/functional/u/undefined/undefined_loop_variable_py38.rc
@@ -0,0 +1,2 @@
+[testoptions]
+min_pyver=3.8